As a result, Medard's Toulouse teammate Clement Poitrenaud, who won the last of his 44 caps in last year's Six Nations defeat by England at Twickenham, has been drafted into the French squad.
Following Medard's confirmed absence, Saint-André has opted to delay naming his starting XV until Wednesday but after admitting his options at full-back are now limited, Poitrenaud is expected to start.
"We don't have a lot of full-backs in the squad. We chose Clement Poitrenaud even though we had one or two other options," said Saint-André.
"We will leave naming the team until Wednesday instead of Tuesday to see how the players recover from their efforts (against Scotland).
"We also want to take another look at our next opponents as Ireland have also played another game having defeated Italy (on Saturday)."